Executive summary

Purpose of intervention

This report records the findings of my intervention visit to Hinkley Point B (HPB) Nuclear Power Station ahead of Reactor 4 (R4) Outage Number 029, 2015 periodic shutdown. The intervention was undertaken to confirm the adequacy of mechanical engineering related activities conducted by the Licensee to comply with the requirements of Licence Condition 28, examination, inspection, maintenance and testing (EIMT) against a sample of nuclear safety significant reactor components.

Interventions Carried Out by ONR

The intervention consisted of on-site meetings and a plant inspection with relevant staff from EDF Energy, Nuclear Generation Limited (NGL) to determine the adequacy of the work being undertaken on R4 in complying with the requirements of Licence Condition 28. The activities examined were selected as follow up from a visit in November 2014 and due to their nuclear safety significance. The inspection included:

EIMT of gas circulators (GCs)

EIMT of control rod assemblies (CRA) and super articulated control rods (SACR);

EIMT of valves ;

Preparations for outage specific activities and follow up of event learning from experience.

The inspection was supported by inspection visits to the following areas:

Contractor valve maintenance facility [non active].

The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

I concluded from the inspection of GC’s on the basis of my sampling the 3 GC’s prepared for the R4 2015 outage have been subject to adequate EIMT consistent with the expectations of LC28. The GC lubrication oil pump and motor replacement components were on plan and did not appear to pose a threat to return to service. The NGL response to an inlet guide vane operational finding was adequate and the outcomes will be followed up as part of routine regulatory business.

I concluded from the inspection of CRA rod drop performance during shutdown for the R4 2015 outage, the results were in line with safety case performance assumptions and entirely consistent with previous test results underpinning confidence in CRA drop reliability. The SACR drop performance was consistent with the general population of control rods. It is my judgement overall the CRA rod drop performance is satisfactory and confirms performance reliability giving me confidence the EIMT for CRA is consistent with the expectations of LC28.

I concluded from my inspection of EIMT of valves I was satisfied they are subject to adequate EIMT in support of the return to service following the R4 2015 statutory outage and are consistent with the expectations of LC28. I intend following up separately with the NGL Chief Mechanical Engineer at Barnwood under my routine L4 engagements and as routine regulatory business, following confirmation at other stations, the arrangements for establishing a systematic and consistent approach in determining EIMT requirements for valves which have a nuclear safety significant function.

I concluded from my inspection of the contractor’s valve maintenance facility undertaking EIMT of valves important to nuclear safety requires improvement over the longer term to meet relevant good practice and the expectations of NGL foreign material exclusion specification. However, it is my judgement on the basis of the sample taken that the EIMT activities were being undertaken to a broadly adequate standard by knowledgeable personnel. Taking in to account the improvements I judge are necessary to meet relevant good practice, the EIMT of valves meets the minimum expectations of LC28.

I intend following up as routine regulatory business the GC 18A investigation outcome and improvement to the Contractors valve maintenance facility with NGL. I also intend providing ONR assessment colleagues with further details of findings from my inspection which fall within their area of expertise for further follow up.

Conclusion of Intervention

This report presents the findings of the mechanical engineering intervention of the LC28 EIMT arrangements in place to support the Hinkley Point B R4 029 2015 periodic shutdown.

After consideration of the findings from the intervention I judge that the LC28 arrangements in place are broadly adequate and I am satisfied they are generally adequately implemented.

I have concluded for LC28 EIMT for this intervention an IIS Rating – 3 adequate overall. I am satisfied NGL demonstrated broadly an adequate level of LC28 compliance and their arrangement meet ONR's guidance. The opportunity for improvements under ALARP associated with NGL specification for FME and additional shortfalls against relevant good practice in the Contractor valve maintenance facility was a small part of the overall inspection and I am satisfied overall all other areas of inspection were adequate.